scholarly journals Preparation and properties of magnesite aggregate radiation - proof concrete

2018 ◽  
Vol 175 ◽  
pp. 01003
Author(s):  
Bingquan Sun ◽  
Jiajia Sun
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Pore Structure ◽  
Water Content ◽  
Radiation Protection ◽  
Point Of View ◽  
Crystal Water ◽  
Ordinary Concrete ◽  
Mixing Water

This paper, from the point of view of improving compactness of density and crystal water content of radiation-proof concrete, using magnesite with high crystal water content as aggregate and alkaline potential water as mixing water, prepared ordinary density radiation-proof concrete and studied its mechanical properties, resistivity and pore structure. The results show that, compared to base ordinary concrete, the prepared concrete has better 28d compressive strength and resistivity, overall porosity decreases by 17%, and pore gradation at all ages improves significantly. It is indicated that the prepared magnesite aggregate radiation concrete has good density and durability, improves concrete radiation protection performance.

scholarly journals Effects of Bacillus subtilis biocementation on the mechanical properties of mortars

2019 ◽  
Vol 12 (1) ◽  
pp. 31-38 ◽  
Author(s):  
N. SCHWANTES-CEZARIO ◽  
M. F. PORTO ◽  
G. F. B. SANDOVAL ◽  
G. F. N. NOGUEIRA ◽  
A. F. COUTO ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Calcium Carbonate ◽  
Cementitious Materials ◽  
Mechanical Analysis ◽  
Sem Analysis ◽  
Subtilis Strain ◽  
Cement Mortars ◽  
Water To Cement Ratio ◽  
Mixing Water

Abstract This study aims to evaluate the influence of B. subtilis AP91 spores addition on the mechanical properties of mortars. B. subtilis strain AP91, isolated from rice leaves of the needle variety, which has an early cycle of production, was used at the concentration of 105 spores/mL in mortars with cement-to-sand ratio of 1:3 (by weight) and water-to-cement ratio (w/c) of 0.63. These spores were added in two different ways: in the mixing water and by immersion in a solution containing bacterial spores. Scanning Electron Microscope (SEM) analysis showed crystals with calcium peaks on the EDS, which possibly indicates the presence of bioprecipitated calcium carbonate. The results obtained in the mechanical analysis showed that the bioprecipitation of CaCO3 by B. subtilis strain AP91 was satisfactory, particularly when the spores were added in the mixing water, increasing the compressive strength up to 31%. Thus, it was concluded that the addition of B. subtilis AP91 spores in the mixing water of cement mortars induced biocementation, which increased the compressive strength. This bioprecipitation of calcium carbonate may very well have other advantageous consequences, such as the closure of pores and cracks in cementitious materials that could improve durability properties, although more research is still needed on this matter.

The Influence of Pore-Strucrure on the Campressive Strength of Hardened Cement Paste

1984 ◽  
Vol 42 ◽  
Author(s):  
Huang Yiun-Yuan ◽  
Ding Wei ◽  
Lu Ping
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Pore Structure ◽  
Cement Paste ◽  
Total Porosity ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
New Information ◽  
The Relationship ◽  
Empirical Constants

AbstractThe pore-structure strongly influences the carpressive strength of hardened cement paste (hcp) and other porous materials, as well as other mechanical properties. The simplest but most currently used expression representing the relationship between the pore-structure and compressive strength is fram Balshin: σ = σ0 (l-P)A, in which only the total porosity P is involved as a single parameter and σ0 and A are empirical constants. The influence of pore size distribution and pore shapes etc. are not considered.The authors introduce second parameter w - the factor of relative specific surface area of the pores other than the total porosity P into consideration and a new expression is proposed:σc=K11-p/1+2p(K2(1-p))K3w+K4 all the constants K1 - K4 can be determined experimentally. By using of this expression the new information relating the influence of pore-structure on the caopressive strength of hcp can be predicted.

Comparison of Porous Ti6Al4V Made by Sponge Replication and Directly 3D Fiber Deposition and Cancellous Bone

2007 ◽  
Vol 330-332 ◽  
pp. 999-1002 ◽  
Author(s):  
J.P. Li ◽  
J.R. Wijn ◽  
Clemens A. van Blitterswijk ◽  
K. de Groot
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Pore Structure ◽  
Cancellous Bone ◽  
Structure And Properties ◽  
Porous Ti ◽  
Fiber Deposition ◽  
Regular Open

The present investigation gives a comparison of the structure and properties of porous Ti6Al4V made by sponge replication (Sponge Ti) and directly 3D fiber deposition (D3DF Ti) and cancellous bone. Although the macrostructure of these two materials differs, their microstructure seems to be similar. Both scaffolds reveal an open pore structure, while D3DF Ti shows a fairly regular open pore structure, sponge Ti6Al4V exhibit an irregular open pore structure similar to that of cancellous bone. The mechanisms resulting in mechanical properties like stiffness or strength are, accordingly, different. The compressive strength and E’ modulus of Ti6Al4V scaffold are higher than that of cancellous bone,. The permeability results show both Ti6Al4V scaffolds are quite comparable with cancellous bone.

Evaluation of Relations among Basic Mechanical Properties of Concrete with Machine-Made Sand

2011 ◽  
Vol 418-420 ◽  
pp. 441-444 ◽  
Author(s):  
Feng Lan Li ◽  
Yan Zeng ◽  
Chang Yong Li
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Flexural Strength ◽  
Rough Surface ◽  
Design Code ◽  
Ordinary Concrete ◽  
Axial Compressive Strength ◽  
Different Characteristics

Due to many different characteristics such as irregular polygon particle with pointed edges, rough surface and larger content of stone powder, machine-made sand has ignorable effects on the properties of concrete. As the basis for the design of concrete structures, the relations among the basic mechanical properties of concrete such as compressive strength, tensile strength, flexural strength and elastic modulus should be clearly understood. This paper summarizes the test data from the published references, and discusses the relations among these properties by statistical analyses compared with those of ordinary concrete. The results show that the axial compressive strength and the tensile strength can be prospected by the same formulas of ordinary concrete specified in current Chinese design code, but the prospected tensile strength should multiply a reducing coefficient when the strength grade of concrete is lower than C30. The elastic modulus of concrete with machine-made sand is larger than that of ordinary concrete, which should be prospect by the formula in this paper. Meanwhile, the formula of flexural strength is suggested.

Experiment and Mechanism Study on Effect of Water/Binder and Fly Ash on Mechanical Properties of HPC

2011 ◽  
Vol 255-260 ◽  
pp. 3404-3410
Author(s):  
Shuang Xi Li ◽  
An Quan Xu ◽  
Xin Jun Tang ◽  
Quan Hu
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Concrete Strength ◽  
Early Period ◽  
Point Of View ◽  
Mechanism Study ◽  
Compressive Strength Test ◽  
Large Water

It takes on the technical and economic double benefits that fly ash taking the place of cement. However, water/binder of modern concrete is generally low; the research on the concrete performance which is based on large water/binder is no longer suitable for analysis of modern concrete. As to this problem, using different proportions of W/B and FA dosage as influencing factors, specimen is compounded for the compressive strength test. Then, mechanical properties of HPC are studied systematically. Based on this, macro-performance is analyzed from a micro-mechanism point of view through taking the electron micrograph. As the study shows, strength of HPC mixed with fly ash has low characteristics at early period while high ones at later period. At later hydration, fly ash effect plays a significant role, the growth rate of concrete strength increases as the increase of FA dosage. Compressive strength of concrete decreases as the increase of W/B and FA dosage. When the W/B is high, compressive strength is not sensitive to the change of W/B and FA dosage; but when the W/B decreases from 0.30 to 0.25, the concrete strength transition occurs. The influence of W/B on concrete compressive strength is more significant than that of the FA dosage; in the preparation of HPC, fly ash can be added more and cement is added less relatively by decreasing the W/B, displaying the role of micro-aggregate filling and modification, improving the strength and other performance of concrete. The study on micro-mechanism proves well the macro-phenomena above.

Research about the Effect of Polypropylene Fiber on Mechanical Properties of Curing Sludge

2011 ◽  
Vol 250-253 ◽  
pp. 788-794
Author(s):  
Shu Lin Zhan ◽  
Shu Sen Gao ◽  
Jun Ying Lai
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Shear Strength ◽  
Water Content ◽  
Unconfined Compressive Strength ◽  
Polypropylene Fiber ◽  
Physical And Mechanical Properties ◽  
Curing Time ◽  
Strength Tests ◽  
Different Content

In order to study the influence of modified polypropylene (PP) fiber on the physical and mechanical properties of curing sludge, the same amount of cement and different content of polypropylene fiber were mixed into the sludge. Unconfined compressive strength tests, water content tests and shear strength tests were carried out on different specimens with different curing time. The results show that the sludge curing effect is markedly improved by the addition of the polypropylene fiber. As to the curing sludge with the same curing time, when the content of the polypropylene fiber increases, the unconfined compressive strength and the cohesive strength greatly increase, and the internal frictional angle decreases.

Experimental Research on Mechanical Properties of the early-Age Shotcrete

2011 ◽  
Vol 90-93 ◽  
pp. 2188-2192
Author(s):  
Nan Xie ◽  
Jie Ouyang ◽  
Bing Li ◽  
Jing Hui Lu
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Experimental Research ◽  
Early Age ◽  
Construction Sites ◽  
Exponential Relationship ◽  
Construction Period ◽  
Ordinary Concrete ◽  
Under Construction

Abstract. The compressive strength and elastic modulus of early-age shotcrete have important influence on the safety of tunnel during construction period. In order to investigate the laws of the mechanical properties of early-age shotcrete, experiments on the compressive strength and elastic modulus of early-age shotcrete with two different mixes used frequently on construction sites were carried out. The results show that the compressive strength and elastic modulus of shotcrete develop fairly rapidly and especially the development of elastic modulus of shotcrete is faster than that of ordinary concrete. There is an exponential relationship between the compressive strength and time as well as the elastic modulus development and time. Simultaneously their formulas were derived. The research results of this paper are not only helpful to understand the laws of the mechanical properties of early-age shotcrete, but also provide some reference for the reliability analysis of tunnel under construction.

Water Absorption and Mechanical Properties of Cements Based on Poly (Methyl Methacrylate) (PMMA) as Function of Hydroxyapatite (HA) Content

2008 ◽  
Vol 396-398 ◽  
pp. 493-496
Author(s):  
D. Ionita ◽  
G. Tihan ◽  
A.T. Marques
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Methyl Methacrylate ◽  
Water Absorption ◽  
Mechanical Characterization ◽  
Setting Time ◽  
Young Modulus ◽  
Point Of View ◽  
Maximum Strength ◽  
Poly Methyl Methacrylate

The purpose of this study is the obtaining of different orthopedic materials and chemical and mechanical characterization. The chemical tests used were setting time, water absorption and from the point of view of mechanical properties the Young modulus, compressive strength, and maximum strength. Also, the surface of orthopedic bioceramics materials was characterized by porosity test.

scholarly journals Mechanical properties and carbon footprint of 3D-printable cement mortars with biochar additions

2020 ◽  
Vol 323 ◽  
pp. 01017
Author(s):  
Devid Falliano ◽  
Dario De Domenico ◽  
Salvatore Quattrocchi ◽  
Paolo Cosenza ◽  
Giuseppe Ricciardi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Research Work ◽  
Point Of View ◽  
Maximum Diameter ◽  
Future Research ◽  
Cement Mortars ◽  
Fresh State ◽  
High Consistency

This contribution focuses on the design and the characterization of innovative mix designs of high consistency mortars with biochar additions in different percentage with respect to the cement weight. Biochar is a by-product material that gives the cementitious mix a sustainable connotation from an environmental point of view. The mix designs presented here are characterized by a good dimensional stability in the fresh state, peculiarity that gives them the possibility to be extruded and so, to be used in automated construction processes. In addition to the mechanical properties (flexural and compressive strength), the assessment of the CO2 emission of representative mixes is presented. Different biochar content and maximum diameter of the aggregate are studied, obtaining interesting indications on these parameters to optimize mechanical properties. Finally, on the basis of the CO2 emission assessment, certain venues for future research work to minimize CO2 emissions are reported.

scholarly journals Impact of impurities of local construction materials on the bearing capacity of the concrete used in structures in Burundi

Vestnik MGSU ◽  
2021 ◽  
pp. 1357-1362
Author(s):  
Emmanuel Mikerego ◽  
Nestor Niyonzima ◽  
Jean Claude Ntirampeba
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Concrete Structures ◽  
Construction Materials ◽  
Reinforced Concrete Structures ◽  
Ordinary Concrete ◽  
Average Decrease ◽  
Local Construction ◽  
The Impact ◽  
Mixing Water

Introduction. The article is about an assessment of the impact of impurities contained in the local construction materials on the mechanical characteristics of the concrete used in reinforced concrete structures in Burundi. Materials and methods. The methodology of the study consisted in varying the quantity of impurities for the manufactu­ring of the concrete experimental cubic samples. The grain sizes of the studied ordinary concrete were in the favourable zones according to the recommended granulometry for standard concretes. Simulation of impurities was made by adding in the mixing water solid particles taken from a local rock called “red earth”. The particles were composed by (24 %) of clays, (38 %) of silts and (38 %) of sands. As for the used cement in this study, it was the type CEM I (32.5). The quantities of impurities were expressed in grams per litre of mixing water (g/l) and were varying from (0 g/l) to (100 g/l) with a step of (20 g/l). The prepared experimental concrete samples were stored in the laboratory of materials at the University of Burundi and were subjected to compression testing under hydraulic press after 28 days. Results. The impact of impurities consisting of (24 %) of clays, (38 %) of silts and (38 %) of sands is identified. Each increase of (20 g) of impurities in a litre of mixing water induces an average decrease of (4 %) on the compressive strength and the Young’s modulus for an ordinary concrete. Conclusions. The impact of impurities contained in the local construction materials used in the manufacturing of the concrete for reinforced concrete structures in Burundi is studied. Each increase of (20 g) of impurities in a litre of mixing water induces an average decrease of (4 %) on the compressive strength and the Young’s modulus of an ordinary concrete. For Burundi, a curve for the approximation of the bearing capacity of the concrete used in reinforced concrete structures according to the quantity of impurities contained in the local construction materials was established. Hence, it is advisable to start by the specification of the quantity of impurities contained in the construction materials before making the concrete for reinforced concrete structures in order to predict the mechanical performances of the concrete used in reinforced concrete structures.

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